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Abstract

Selectively permeable asymmetric membranes are disclosed which are suitable for use in hemodialysis processes and the like. The membranes are produced from hydrophobic and hydrophilic polymers, and include a three-layered structure including a first dense thin skin layer which includes uniform pores of a size whereby proteins having a molecular weight of at least that of albumin are substantially rejected therefrom, an intermediate second layer in the form of a sponge and having a higher diffusive permeability than the first layer, and a third layer with a finger-like structure which provides mechanical stability. These membranes are preferably formed in the shape of hollow fibers, with the first layer as the inner layer thereof. Processes for manufacturing these membranes are also disclosed, and include separately mixing both the hydrophobic and hydrophilic polymers in solvents therefor, and then mixing these two solutions before extruding the mixture into a precipitating liquid to form the precipitated membrane by a wet-phase inversion technique.

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First Claim